The Joint Typhoon Warning Center– a joint United States Navy– United States Air Force task force – also issues tropical cyclone warnings for the region.[5] Wind estimates from Météo-France and most other basins throughout the world are sustained over 10minutes, while estimates from the United States-based Joint Typhoon Warning Center are sustained over 1minute. 1-minute winds are about 1.12 times the amount of 10-minute winds.[6]

If a tropical storm in the basin strengthens to attain 10minute sustained winds of at least 118km/h (74mph), the MFR classifies it as a tropical cyclone, equivalent to a hurricane or typhoon (a use of "tropical cyclone" which is more restrictive than the usual definition).[7]

History of the basin

The first storm in the MFR database of the basin originated on January11, 1848. In January1960, the first named storm was Alex, and each subsequent year had a list of storm names. Beginning in 1967, satellites helped locate cyclones in the basin, and in the following year, the MFR began estimating storm intensities from the satellite images. By 1977, the agency was using the Dvorak technique on an unofficial basis, but officially adopted it in 1981. Originally, the basin only extended to 80°E, and while it was extended eastward to the current 90°E, a lack of satellite imagery initially made data uncertain east of 80°E. The World Meteorological Organization designated the MFR as a Regional Tropical Cyclones Advisory Centre in 1988, and upgraded it to a Regional Specialized Meteorological Center in 1993. In May 1998, two Europe-based Meteosat satellites began providing complete coverage of the basin. On July1, 2002, the MFR shifted the cyclone year to begin on this date and end on June30 of the following year; previously, the cyclone year began on August1 and ended on the subsequent July31. In 2003, the MFR extended their area of warning responsibility to 40°S, having previously been limited at 30°S.[2] During 2011, MFR started a reanalysis project of all tropical systems between 1978–98, with methods such as a Dvorak technique reanalysis and use of microwave imagery.[8] Preliminary results from this reanalysis project include correcting an increasing trend in the number of very intense tropical cyclones in the basin since 1978.[8] This also revealed a seemingly systematic underestimation of tropical cyclone intensities in the past.[8]

Statistics

From the 1980–81 to the 2010–11 season, there was an average of 9.3tropical storms each year in the basin. A tropical storm has 10minute winds of at least 65km/h (40mph). There are an average of five storms that become tropical cyclones, which have 10 minute winds of at least 120km/h (75mph).[9] As of 2002, there was an average of 54days when tropical systems were active in the basin, of which 20 had tropical cyclones active, or a system with winds of over 120km/h (75mph). The median start date for the season was November17, and the median end date was April20.[1]

Climatology

Tracks of storms in the basin from 1980 to 2005

Generally, the monsoon does not cross into the Mozambique Channel until December; as a result, storms rarely form there before that time.[1] From 1948 to 2010, 94tropical systems developed in the small body of water, of which about half made landfall.[10] Occasionally, small storms form in the Mozambique Channel that resemble Mediterranean tropical cyclones or storms in the northeastern Atlantic Ocean; these systems are well-organized but have weaker convection than typical tropical cyclones, and originate over cooler than normal water temperatures of less than 26°C (79°F). A survey in 2004 conducted by weather expert Gary Padgett found meteorologists split whether these storms should be classified as tropical or subtropical.[11]

In an average year, ten tropical depressions or storms strike Madagascar, and most generally do not cause much damage.[12] Occasionally, storms or their remnants enter the interior of southeastern Africa, bringing heavy rainfall to Zimbabwe.[13]

Notes

Related Research Articles

Tropical cyclones and subtropical cyclones are named by various warning centers to provide ease of communication between forecasters and the general public regarding forecasts, watches, and warnings. The names are intended to reduce confusion in the event of concurrent storms in the same basin. Generally once storms produce sustained wind speeds of more than 33 knots, names are assigned in order from predetermined lists depending on which basin they originate. However, standards vary from basin to basin: some tropical depressions are named in the Western Pacific, while tropical cyclones must have a significant amount of gale-force winds occurring around the centre before they are named in the Southern Hemisphere.

Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basin(s) they are located in. Only a few scales of classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but some alternative scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index.

A Regional Specialized Meteorological Centre is responsible for the distribution of information, advisories, and warnings regarding the specific program they have a part of, agreed by consensus at the World Meteorological Organization as part of the World Weather Watch.

The 2005–06 South-West Indian Ocean cyclone season was the fifth least-active on record. The Météo-France office on the island of Réunion tracked 13 tropical disturbances, of which six intensified into a moderate tropical storm. Three of these systems proceeded to attain tropical cyclone status – reaching 10 minute maximum sustained winds of at least 120 km/h (75 mph). The American-based Joint Typhoon Warning Center also tracked eight storms in the basin. Activity was below normal due to a powerful Walker circulation, which increased convection over the neighboring Australian basin, but suppressed activity in the western Indian Ocean. As a result, most of the storms developed near or entered from the Australian basin, crossing 90°E to enter the South-West Indian Ocean.

The 2004–05 South-West Indian Ocean cyclone season was a near average season, despite beginning unusually early on August 30 with the formation of an early-season tropical depression. Météo-France's meteorological office in Réunion (MFR) ultimately monitored 18 tropical disturbances during the season, of which 15 became tropical depressions. Two storms – Arola and Bento – formed in November, and the latter became the most intense November cyclone on record. Bento attained its peak intensity at a low latitude, and weakened before threatening land. Tropical Cyclone Chambo was the only named storm in December. In January, Severe Tropical Storm Daren and Cyclone Ernest existed simultaneously. The latter storm struck southern Madagascar, and five days later, Moderate Tropical Storm Felapi affected the same area; the two storms killed 78 people and left over 32,000 people homeless. At the end of January, Severe Tropical Storm Gerard existed as an unnamed tropical storm for 18 hours due to discrepancies between warning centers.

The 2001–02 South-West Indian Ocean cyclone season had the earliest named storm since 1992. Many storms formed in the north-east portion of the basin, and several more originated around Australia. The basin is defined as the waters of the Indian Ocean west of longitude 90°E to the coast of Africa and south of the equator. Eleven tropical storms formed, compared to an average of nine. Tropical systems were present during 73 days, which was significantly higher than the average of 58 for this basin.

The 2008–09 South-West Indian Ocean cyclone season was a slightly above average event in tropical cyclone formation. It began on November 15, 2008, and officially ended on April 30, 2009, with the exception for Mauritius and the Seychelles, for which it ended on May 15, 2009. These dates conventionally delimit the period of each year when most tropical cyclones form in the basin, which is west of 90°E and south of the Equator. Tropical cyclones in this basin were monitored by the Regional Specialised Meteorological Centre in Réunion.

Intense Tropical Cyclone Bondo was the first of a series of six tropical cyclones to impact Madagascar during the 2006–07 South-West Indian Ocean cyclone season. Bondo developed on December 15 in the central Indian Ocean, west of Diego Garcia. After strengthening into a moderate tropical storm on December 18, the storm rapidly intensified while moving westward, taking advantage of favorable atmospheric conditions. Within 18 hours of being named, Bondo intensified to tropical cyclone status, or the equivalent of a minimal hurricane. The Météo-France office on Réunion (MFR) estimated peak 10 minute sustained winds of 205 km/h (125 mph), although the American-based Joint Typhoon Warning Center estimated stronger 1 minute winds of 250 km/h (155 mph). While near peak intensity, Bondo passed just south of Agaléga island, before weakening slightly and moving through the Farquhar Group of islands belonging to the Seychelles, becoming the strongest cyclone to affect that island group in decades. Bondo turned southwestward, and after brushing the northern coast of Madagascar, the cyclone made landfall near Mahajanga on December 25. The storm continued southward, and was last tracked by the MFR on December 28.

The 2009–10 South-West Indian Ocean tropical cyclone season was a near average event in tropical cyclone formation. the season officially started on July 1, 2009, and ended on June 30, 2010, after incorporating the tropical cyclone season which ran from November 1 to April 30 for all areas except for Mauritius and the Seychelles, for which it ended on May 15, 2010. In this basin which officially runs from 30 to 90E and is to the south of the equator, the main warning center is the Regional Specialized Meteorological Center on La Reunion Island; however they delegate the naming of Cyclones to the Meteorological services of Mauritius and Madagascar.

The 2010–11 South-West Indian Ocean cyclone season was the least active cyclone season on record in the basin, tied with 1982–83, producing only four systems of gale intensity. This was due to cooler than normal water temperatures and the Walker circulation – a broad atmospheric circulation – causing unusually moist conditions in the eastern Indian Ocean and unusually dry conditions in the western Indian Ocean. The basin includes the waters of the ocean south of the equator and west of 90º E to the eastern coast of Africa.

The 1982–83 South-West Indian Ocean cyclone season was least active cyclone season in the basin since 1961–1962. There were six systems that were named, although three of them – Arilisy, Clera, and Fely – failed to intensify beyond tropical depression status. No storms reached tropical cyclone status, according to the official warning agency for the basin, Météo-France, although the two strongest storms – Bemany and Elinah – peaked just below that intensity. The first named storm, Arilisy, formed on October 27, and dissipated without having affected land. However, the Joint Typhoon Warning Center (JTWC), which is an unofficial warning center for the basin, briefly tracked a tropical depression in July. The next storm was Bemany, which passed east of Mauritius near peak intensity in early December. Tropical Depression Clera existed briefly in the middle of September, and Tropical Storm Dadafy moved across the eastern portion of the basin in late December.

The 2012–13 South-West Indian Ocean cyclone season was a slightly above average event in tropical cyclone formation in the Southern hemisphere tropical cyclone year starting on July 1, 2012, and ending on June 30, 2013. Within this basin, tropical and subtropical disturbances are officially monitored by the Regional Specialised Meteorological Centre on Réunion island, while the Mauritius and Madagascar weather services assign names to significant tropical and subtropical disturbances. The first tropical disturbance of the season developed on October 12 and rapidly developed into the earliest known intense tropical cyclone on record during October 14.

The 2013–14 South-West Indian Ocean cyclone season was an above average event in tropical cyclone formation. The season officially began on July 1, 2013, though the first tropical system designated by Météo-France was a short-lived tropical disturbance that developed on July 8. However, the first named storm was Cyclone Amara in December. Bruce was the first very intense tropical cyclone since Edzani in 2010, which originated from the Australian region. The strongest system of the cyclone season was Hellen, also one of the most intense tropical cyclones over the Mozambique Channel. The season officially ended on June 30, 2014

The 2014–15 South-West Indian Ocean cyclone season was an above average event in tropical cyclone formation. It began on November 15, 2014, and ended on April 30, 2015, with the exception for Mauritius and the Seychelles, for which it ended on May 15, 2015. These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of 90°E and south of the Equator. Tropical and subtropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in Réunion.

The 2015–16 South-West Indian Ocean cyclone season was a slightly below average event in tropical cyclone formation. The annual cyclone season began on November 15, 2015, with the first storm, Annabelle, forming four days following. The final and strongest storm, Fantala, dissipated on April 23, 2016, a week before the season ended on April 30 for most of the region. In Mauritius and the Seychelles, the cyclone season ended half a month later, on May 15. The season's activity was influenced by an ongoing El Niño, and a positive Indian Ocean Dipole.

The 2016–17 South-West Indian Ocean cyclone season was a below-average season, with five tropical storms, three of which intensified into tropical cyclones. It officially began on November 15, 2016, and ended on April 30, 2017, with the exception for Mauritius and the Seychelles, for which it ended on May 15, 2017. These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of 90°E and south of the Equator. Tropical and subtropical cyclones in this basin were monitored by the Regional Specialised Meteorological Centre in Réunion, though the Joint Typhoon Warning Center issued unofficial advisories.

The 2018–19 South-West Indian Ocean cyclone season was the costliest and the most active season ever recorded since reliable records began in 1967. Additionally, it is also the deadliest cyclone season recorded in the South-West Indian Ocean, surpassing the 1891–92 season, in which the 1892 Mauritius cyclone devastated the island of Mauritius. The season was an event of the annual cycle of tropical cyclone and subtropical cyclone formation in the South-West Indian Ocean basin. It officially began on November 15, 2018, and ended on April 30, 2019, with the exception for Mauritius and the Seychelles, which it ended on May 15, 2019. These dates conventionally delimit the period of each year when most tropical and subtropical cyclones form in the basin, which is west of 90°E and south of the Equator. Tropical and subtropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in Réunion.

Intense Tropical Cyclone Kenneth was the strongest tropical cyclone to make landfall in Mozambique since modern records began. The cyclone also caused significant damage in the Comoro Islands and Tanzania. The fourteenth tropical storm, record-breaking tenth tropical cyclone, and tenth intense tropical cyclone of the 2018–19 South-West Indian Ocean cyclone season, Kenneth formed from a vortex that the Météo-France office on La Réunion (MFR) first mentioned on 17 April. The MFR monitored the system over the next several days, before designating it as Tropical Disturbance 14 on 21 April. The disturbance was located in a favorable environment to the north of Madagascar, which allowed it to strengthen into a tropical depression and later a tropical storm, both on the next day. The storm then began a period of rapid intensification, ultimately peaking as an intense tropical cyclone with 10-minute sustained winds of 215 km/h (130 mph) and a minimum central pressure of 934 hPa. At that time, Kenneth began to undergo an eyewall replacement cycle and weakened slightly, before making landfall later that day as an intense tropical cyclone. As a result of land interaction, Kenneth became disorganised as it made landfall and rapidly degenerated thereafter. The storm then shifted southward, with the MFR cancelling all major warnings for inland cities. Kenneth was reclassified as an overland depression after landfall, with the MFR issuing its warning at midnight UTC on 26 April. Thunderstorm activity developed off the coast of Mozambique on 27 April as the system began drifting northward. Kenneth re-emerged off the coast of northern Mozambique on 28 April, before dissipating on the next day.